Hardly something to murder someone over, or even sending threats via the Internet, which can also put you into legal trouble. I'm also glad you don't carry if that's what sets you off.

To the OP, your return process seems to be overly generous to the buyer. If he stated in writing his reason for the request was because he found it cheaper, did you state the return would only be granted based on the return of new unused parts? Even if eBay would grant a refund, why send the money before you had parts in hand?

If you have his responses in writing and your stipulations on the return, would eBay really ignore a box of junk being returned?